The present invention relates to battery monitoring, and more particularly, to methods, apparatus and program products for estimating battery reserve life.
The valve regulated lead acid (VRLA) battery is used extensively throughout the telecommunications industry as a backup energy storage source. Typically, the battery is the only backup energy source in such applications and, thus, the last line of defense against system failure in the event of AC mains failure. Due to mis-operation, manufacturing deficiencies or the lack of monitoring and maintenance, it is often the most unreliable component within the standby power system.
Battery capacity, the energy storage capability, has long been a target of researchers as a definitive battery state of health (SOH) indicator. Conventional standards, such as “IEEE Recommended Practices for Maintenance, Testing and Replacement of Valve Regulated Lead Acid (VRLA) Batteries in Stationary Applications,” IEEE STD 1188-1996, base criteria for determining end of battery operational life on capacity. Typically, when the capacity reaches 80% of the manufacturer's rated capacity, the battery is deemed to be at the end of its operational life.
Although much work has been conducted to develop algorithms to determine battery SOH, it appears that little work has been performed to develop techniques for estimating battery reserve life. The ability to determine that a battery is not able to perform as required has obvious advantages. However, this information often comes too late, such that system performance may be jeopardized and may remain that way until the old battery can be replaced, which may take many weeks. Accordingly, there is a need for effective techniques for predicting battery reserve life.